Another new year, another new diet book. This time it's from Esther Blum, New York dietician to the stars - allegedly Sarah Jessica Parker and Teri Hatcher.

It promises a route to gorgeousness that has taken America by storm because it promotes eating fats (even saturated ones) and having fun. Blum says nothing is off limits in moderation, that fat-free diets have messed up women's hormones and that saturated fats make you feel fuller for longer.

The best way to start a day the Blum way is with a vegetable omelette - using yolks - with strawberries on the side. Her book Secrets of Gorgeous: Hundreds of Ways to Live Well While Living It Up was published on Christmas Eve in America and will be coming to Britain in January. Here, it will join the 35,000-plus diet books on Amazon, reflecting our enormous appetite for losing weight. Dr Atkins' New Diet Revolution alone has sold more than 10m copies worldwide.

Surveys show that two out of five women are dieting most of the time (the figure for men is slightly lower, at 18%) which may be because studies show that half of the weight lost is regained in a year.

Our belief in dietary regimens is not new. In 1087 William the Conqueror is reputed to have gone on a liquid diet to lose weight and Lord Byron lost more than three stone on the vinegar diet. Most diets, however wacky, will work in the short term (defined as losing weight in the first few months) if you stick to them.

The cabbage diet, for example, works because no one wants to eat cabbage. A study in the British Medical Journal (which was randomised and had a control group of non-dieters) found that the four diets it looked at - Atkins, Slim-Fast, Weight Watchers and Rosemary Conley - all worked, with people who stuck to their diets losing an average of 5.9kg (13lb) over six months.

Dieting, however it is dressed up, is not mysterious. You simply have to eat less than the energy that you expend. A diet should be well balanced and have 500 to 600 calories less than your recommended intake, which should make you lose 0.5kg (1lb) a week. Exercise helps, if only because you can't graze on a treadmill.

However, maintaining your new weight is more challenging. A paper in American Psychologist, which examined 31 studies, concluded that diets didn't work, with two-thirds of people putting on more weight than they lost within two years.

Losing weight requires changes to lifestyle and is best done through small and achievable changes, such as going for brisk walks, having regular meals, practising moderation (not too much alcohol, sugar or fat) and eating healthily; remembering to eat five portions of fruit and vegetables a day.

The British Dietetic Association recommends planning your shopping to avoid only having crisps for breakfast and says you shouldn't eat while watching TV or reading. All of which is sensible advice and none of which would make a bestselling diet book.